Many devices require that various amounts of mercury be included therein for their operation. Such a device is the arc discharge lamp which comes in many varieties. Virtually all of these lamps employ mercury as one of the vaporizable components. In current commercial lamps, such as fluorescent lamps, it is common practice to mechanically dispense a drop of natural mercury into the lamp.
This practice of mechanically dispensing mercury or other material works well because natural mercury is a fairly inexpensive commodity costing about $0.30/gram. A mercury droplet can be placed within a small capsule which is placed in a lamp and opened after the lamp is sealed. See U.S. Pat. No. 3,913,999.
Recently it has been determined that the efficiency of low pressure mercury-rare gas discharge lamps can be enhanced if the isotopic mixture of the mercury is changed from that which occurs naturally. See, for example, Electric Discharge Lamps, MIT Press, 1971, by J. Waymouth for basic principles of low pressure mercury rare gas discharge lamps and U.S. Pat. No. 4,379,252. The latter patent teaches efficiency gains in fluorescent lamps when the .sup.196 Hg isotope is increased from its natural occurrence of about 0.14% to about 3%.
The problem of employing such altered compounds of mercury lies in their expense. For example, at current prices, mercury which has been enhanced to contain 35% of the .sup.196 Hg isotope, costs about $500/milligram (mg). Accordingly, it can be seen that use of this material requires very strict controls on the amount of Hg employed. Further, such materials need only be used in submilligram amounts. Nearly isotopically pure .sup.i HgO (85 to 96%, excluding .sup.196 HgO which is generally 25 to 50% pure) can be mixed in milligram or larger quantities, and then thermally decomposed to form milligram quantities of liquid mercury. In order to reach a particular isotopic distribution, a definite amount of each .sup.i HgO powder must be metered and combined with other isotopically pure .sup.i HgO. With small quantities of HgO, this can be a difficult and time consuming process.
Additional, thermal decomposition requires elevated temperatures T&gt;500.degree. C. Under high vacuum conditions, this process can easily result in the introduction of trace impurities into mercury. Furthermore, vacuum baking at high temperatures requires hardware and techniques that are very complex.